1. Field of the Invention
The present invention relates to ambulatory devices for physically handicapped individuals and, more particularly, this invention relates to an ambulatory wheelstand and to an interface for adapting the wheelstand frame for conversion to a wheelchair.
2. Description of the Prior Art
Ambulatory devices have been used to enable a non-ambulatory person, such as a paraplegic or a quadriplegic, to move about more or less on his own. Typical wheelchairs were the first types of ambulatory devices, but required the user to remain in one position, thus causing atrophy of the muscles.
Wheelstands first resembled a cross between a wheelchair and a gurney and employed a foldable or a pivotable stretcher portion which could pivot between a horizontal and an upright position. Examples of these earlier wheelstands can be found in U.S. Pat. Nos. 2,295,006 to Phillips and 2,986,200 to Nobile. Each of these patents discloses a device having a large central driving wheel rotatably attached to a frame stabilized by castor wheels at the front and the rear of the device. The patient support is pivotably secured to the frame and includes either a straight stretcher or a somewhat chair-shaped platform to support the user. The support is pivotable between an upright position and a horizontal position. Because of the relatively high pivoting point of the support structure of these devices, the center of gravity of the devices is quite high, rendering the device somewhat unstable. The front and rear castor wheels are required to improve stability.
U.S. Pat. No. 4,310,167 to McLaurin disclosed what the inventor calls a center of gravity wheelchair with an articulated chassis. This wheelchair also has a large drive wheel centrally located and both front and rear castor wheels. The chassis is articulated so that the user can shift the center of gravity of the device forward by operation of a lever which extends the chassis frame and the front castor wheel, thus elongating the frame and improving the stability. This device is particularly useful for negotiating curbs, hills or the like. However, McLaurin still employs front and rear castors and requires the user to assume a sitting position only.
Two improved ambulatory wheelstands are disclosed in U.S. Pat. Nos. 4,620,714 and 4,927,167, both to Davis. The '714 patent discloses a wheelstand having a generally rectangular main frame supported on a ground support surface by two relatively large wheels disposed between a pair of relatively small rear wheels and a pair of relatively small front wheels. The '167 patent also discloses a wheelstand having a user support structure pivotably mounted on a frame.
While these early inventions all played a part in improving the conditions of non-ambulatory persons, they have failed to provide for the specific needs of certain afflicted individuals. The wheelstands that comprise the prior art have utility for many physically handicapped persons, but nevertheless fail to provide for the specific needs of certain afflicted individuals. More particularly, the known wheelstands provide only minimal support for individuals suffering from one of the various cerebral palsy syndromes. These individuals require special trunk and leg support. Even more specific needs are had by those persons grouped in the spastic syndrome. These individuals make up about seventy percent of cerebral palsy cases. The spastic patient requires special care because the affected limbs of the patient usually show increased deep tendon reflexes and muscular hypertonicity and a tendency to contractures. The muscles controlling the limbs tend to contract spontaneously, causing spastic torso and limb movements. None of the known wheelstands are capable of responding to these special needs.
These and other disadvantages are overcome by the invention presented in my copending parent application, Ser. No. 08/002,146 filed Jan. 11, 1993, now issued as U.S. Pat. No. 5,340,139 which discloses an ambulatory wheelstand having special trunk and leg supports necessary to enable individuals afflicted with certain neurological disorders to independently ambulate in the upright position or crawl while lying prone to the floor. The ambulatory wheelstand of that invention comprises a frame including a pair of lateral supports in a spaced, parallel arrangement, each having a horizontally disposed tube or rail with front and intermediate cross supports extending between the lateral supports. A pair of large drive wheels are rotatably secured at the rear end of the lateral supports and a pair of castor wheels are secured to the front end of the lateral supports. A user support structure or prone board comprising a pair of elongated rails spanned at one end by a chest pad is pivotably secured to the lateral supports for pivoting between at least an upright or vertical position and a prone or horizontal position.
The stability of a wheelstand of this type depends on the position of the center of gravity of the device combined with its users. The center of gravity is ideally located as close to the ground as possible and, with respect to the front and rear of the frame, should be located between the drive wheels and the castor wheels, but closer to the drive wheels than to the castor wheels. The center of gravity does not move forward significantly when the prone board is shifted from the upright to the prone position. Instead, the center of gravity remains distributed over substantially the same location of the frame regardless of the position of the prone board. This is accomplished by sliding the prone board rearwardly as it is pivoted from the upright to the prone position. An elongated slot is provided for this purpose in each of the lateral supports. Hinge pins secured to the elongated rails of the prone board are slidably entrained in the slots. A pair of gas cylinders are provided between the prone board and each of the lateral supports. In the upright position of the prone board, the hinge pins are disposed at the forward ends of the elongated slots. As the prone board pivots to the prone position, the hinge pins slide rearwardly to the rear ends of the slots and the pivot arms pivot from an upright position to a more rearward, more horizontal position.
An important feature of the invention disclosed in this parent application lies in its improved system for maintaining spinal alignment, particularly those with a spastic syndrome. In addition to the chest pad, the system comprises a pair of adjustable knee pads and a posterior pelvic stabilizer, or an elongated, curved saddle pivotably attached to a "goose neck" bar. The bar is rigidly attached to the prone board. The stabilizer is movable from a horizontal position that allows the user to mount or dismount the wheelstand to a substantially vertical position in which forward pressure is applied to the back of the pelvis, thereby pressing the user against the chest pad and the knee pads of the prone board.
A pair of optional thoracic lateral pads extend from the sides of the chest pad to stabilize the trunk laterally and to support the trunk in the midline position. Also optionally provided is a posterior thoracic panel for attachment to the lateral pads by a strap and an anterior abdominal pad. At the end of the prone board opposite the chest pad are provided foot plates. In an alternate embodiment, the foot plates may be left off, thereby converting the wheelstand into a walker having all of the trunk support provided in the preferred embodiment.